The engine immobiliser system is designed to prevent the vehicle from being stolen. This system uses a transponder key ecu that stores the key codes of authorized ignition keys. If an attempt is made to start the engine using an unauthorized key, the ecu sends a signal to the ecm to prohibit fuel delivery and ignition, effectively disabling the engine.

The transponder key coil receives this signal, the transponder key amplifier amplifies it, and then the signal is transmitted to the ecu. The ecu matches the key's id code with the vehicle's id code, which was previously registered in the ecu and then communicates the results to the ecm using sfi communication.
Engine immobiliser system
How to proceed with troubleshootingToyota Safety Sense 2.5
The Toyota Safety Sense
2.5 consists of the following
drive assist systems and
contributes to a safe and
comfortable driving experience:
Driving assist system
PCS (Pre-Collision System)
LTA (Lane Tracing Assist)
AHB (Automatic High
Beam)
RSA (Road Sign Assist) (if
equipped)
Dynamic radar cru ...
Rear bumper
Components
Removal
Remove rear bumper cover
Remove the 9 screws and 7 clips.
Put protective tape under the quarter panel.
Detach the 12 claws and remove the bumper cover.
Remove rear bumper protector
Hint:
When removing the bumper protector, heat the bumper
prot ...
Check 4wd control ecu (for 4wd)
Notice:
Turn the ignition switch off before measuring the
resistances of the main wire and branch wire.
After the ignition switch is turned off, check that the
key reminder warning system and light reminder
warning system are not in operation.
Before measuring the resistance, leave the ...